Soyuz TMA-12M successfully docks with ISS

Soyuz Commander Alexander Skvortsov, Flight Engineer Oleg Artemyev and NASA’s Steven Swanson – riding in the Soyuz TMA-12M – have finally docked with the International Space Station (ISS) on Thursday. After what was a delayed arrival – caused by a problem with a key burn during what was supposed to be a six hour trip to the Station – the trio docked with MRM-2 at 7:53pm Eastern.

Soyuz TMA-12M:

Following a nominal launch via the Soyuz FG carrier rocket from the Baikonur Cosmodrome in Kazakhstan at 5:17 pm EDT (9:17 pm UTC), the Soyuz TMA-12M was set to result in a six hour trip to the Station. However, a problem with a key burn delayed rendezvous by two days.

As with a number of previous Soyuz and Progress launches, Soyuz TMA-12M was attempting to use the short cut route to the ISS, avoiding the two day journey of the past.

First carried out for a crewed mission by Soyuz TMA-08M, the well practised procedure was initially demonstrated on recent Progress resupply missions.

The desire to dock to the ISS after just six hours stems from the fact that spending two days in the cramped interior of the Soyuz along with two other crewmates is known to be a stressful and uncomfortable time for astronauts and cosmonauts, many of whom are suffering from symptoms of space sickness at the same time.

Thus, being able to go from the ground to the ISS in a single day will be a big advantage to Soyuz crews.

Such a fast rendezvous was never attempted before as it requires extremely precise orbital adjustments from the ISS, and extremely precise orbital insertion by the Soyuz-FG booster, which was only deemed possible following a study conducted last year, which showed that such accuracy was achievable with the existing Soyuz-FG booster and modernized Soyuz TMA-M series spacecraft.

Following the launch of the reliable Soyuz FG rocket – along with a successful orbital insertion shortly thereafter – the Soyuz TMA-12M was immediately tasked with performing the first two engine burns on its first orbit of the Earth, which were pre-programmed into the Soyuz’s on-board computer prior to launch.

On the second orbit, actual orbital parameters were uplinked from a Russian Ground Site (RGS), which allows for a further eight rendezvous burns to be performed over the next five hours of flight.

During this time, the Soyuz crew will be able to unstrap from their Kazbek couches and enter the Orbital Module (BO) to stretch their legs and use the bathroom facilities.

While the crew were expected to dock to the station’s Poisk module less than six hours later at 11:04 pm, a problem during the “Dv3” burn resulted in mission controllers opting to move to a new flight profile that allowed for Soyuz to arrive in two days time.

It was later revealed the 24 second burn did not occur due to an attitude problem with the Soyuz. It is understood the Soyuz TMA-12M’s flight computer didn’t command the spacecraft to proper attitude for DV3 burn, resulting in an automated “no burn” response. This was caused, in part, by an over-performance of the Soyuz FG’s ascent.

With the launch resulting in an apogee that was 20km higher than expected, this changed the requirements for the Soyuz TMA-12M’s burns.

Since dV3 and dV4 burns are meant to correct for booster performance disparities, the onboard computer decided to use its DPO (attitude thrusters) instead of main engine to perform the burn. However – likely due to a software issue, along with the Soyuz being in the wrong attitude – this resulted in no burn taking place.

Controllers opted to move to the back up plan of a two day rendezvous, with all burns relating to this flight profile conducted without issue.

Soyuz eventually arrived without issue, allowing for the trio to be greeted by Expedition 39 Commander Koichi Wakata of the Japan Aerospace Exploration Agency, the first Japanese astronaut to lead an expedition, and Flight Engineers Rick Mastracchio of NASA and Mikhail Tyurin of Roscosmos.

Swanson, Skvortsov and Artemyev will remain aboard the station until mid-September. Wakata, Mastracchio and Tyurin have been aboard the orbital outpost since November 2013 and will return to Earth May 14, leaving Swanson as the Expedition 40 Commander.

It’s been a busy period on board the orbital outpost regardless, with the Station recently involved in a rare debris dodge.

Known as a Pre-Determined Debris Avoidance Maneuver (PDAM), the ISS utilized the new software version (8.07) of Zvezda’s command and control computers – which was loaded at the beginning of December 2013 – to fire the Service Module thrusters to remove a red conjunction threat from a dead weather satellite.

“A PDAM was successfully executed to avoid a piece of space debris (METEOR 2-5) that was tracking as a RED conjunction. This was the first PDAM using the SM 8.07. All systems performed as expected,” noted L2 ISS Status Report information.

Just days later, another threat was evaluated, namely the two Gravity Recovery And Climate Experiment (GRACE) satellites.

“The conjunction is now classified as a high concern. TOPO will begin modeling Pre-Determined Debris Avoidance Maneuver (PDAM) options to ensure that ISS avoids all the conjunctions that are currently modeling. TOPO has confirmed that there is enough margin in the ISS downstream phasing plan to accommodate a PDAM.”

However, as the conjunction threat was further evaluated, it was determined that the threat would pass safely by the ISS. These two satellites are in a decaying orbit and are expected to end their lives in a few years times via a destructive re-entry.

Meanwhile, An alarm of a different sort occurred on the Station this week, as the Station crew were awoken by a false set of warning annunciations.

False alarms can occur on the Station, sometimes caused by dust entering the sensors. However, in this case, the cause was related to a computer fault.

“It is believed the alarms were triggered due to a communication issue between the MRM-2 terminal computer [TBY-1] & the Service Module Central Computer (ЦВМ). CSA-CP readings confirmed that no fire was present. Later in the day, a FGB smoke event was annunciated.